machinery | Twin screw extruders Exploring shear rate effects


Engineers in the Maris Technology Centre in Italy have completed an analysis of dispersion of organic pigment when processed on different twin screw extrusion set-ups. Maris polymer scientist Alessandro


Gallo says the work at the centre involved, among other things, varying the Do/Di ratio of the screws on its equip- ment to see the effects of the shear rate in the dispersion of phthalocyanine organic pigment during the compounding process. “This study arose because, generally, the market focuses on one or


at most two Do/Di’s, but we look at three,” he says. Gallo explains that Maris makes four machine series, two with a Do/Di of 1.55, one with a Do/Di of 1.65 and the fourth with a Do/Di of 1.78. “It was interesting to note that the


phthalocyanine appreciates being processed with an extruder which can produce a high shear rate - always within certain limits to avoid the agglomerates compaction. Therefore a machine having Do/Di of 1.55,” Gallo says.


“This does not mean that phthalocya-


rovings into the extruder. The company says the low energy oscillating action of its Steer OSE elements is able to gently knead the polymer into the continuous fibres with minimal breakage while a special die design enables the fibres to continue into strands that can be cut into medium and long fibre reinforced pellets. The company says the continuous fibre reinforced thermo- plastic can also be extruded directly into sheet for thermoforming or into pipe or profiles for construction applications. Comac says its EBC co-rotating twin-screw extrud- ers are gaining popularity for production of various


Right: This €14m com- pounding


installation at the Neftekhim PP plant in


Kazakhstan is Leistritz’s biggest


compounding project to date


nine cannot be processed with Do/Di different from 1.55 though. We are speaking about optimisation and choice of machines for new installations,” he says.


“Many times we have carried out


modifications of existing lines, for customers who wished to diversify the production, for example producing pearlescent masterbatches by using Do/ Di 1.55 machines, but those solutions always present limitations, typically in productivity versus quality,” he adds. ❙ www.mariscorp.com


types of glass fibre reinforced compounds. It offers system options for production of short and long fibre reinforced granules for injection moulding, as well as for direct compounding of LFTs for compression moulding (D-LFT). “The main advantage of D-LFT is the possibility to


monitor the length of the fibreglass in the mixing chamber of a twin screw. Such technology is useful in order to have a precise monitoring of compound properties of the extruded material,” says Pietro Zanotto, who works in Comac’s export department. ““Another relevant aspect to consider with this kind of technology, related to mechanical properties, is the achievable degree of rigidity with respect to weight, a significantly relevant parameter for automotive parts manufacturers.” Zanotto says compounding lines based on polymers and chopped glass fibre remain the most popular. “Nevertheless, there is growing interest in Comac lines in D-LFT configurations, mainly due to specific markets and demand of producing higher value added products. The two most interesting regions for us are Europe and the Far East,” he adds.


Click on the links for more information: ❙ www.entek.com ❙ www.centuryextrusion.com ❙ www.feddem.com ❙ www.kraussmaffeiberstorff.com ❙ www.coperion.com ❙ www.leistritz.com ❙ www.polimerteknik.com ❙ www.steerworld.com ❙ www.sp-protec.com ❙ www.sinoalloy.com ❙ www.comacplast.com


36 COMPOUNDING WORLD | March 2016 www.compoundingworld.com


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